Peter James releases landmark 20th book in the Brighton-based Detective Superintendent Roy Grace series

Pretty good going for what started as a two-book deal in which Peter expected to introduce Grace in book one and return to him just the once.

“I never dreamt that I would now be writing the 21st. I think my readers have been very kind to me and very generous to me but I do also think part of the success is that I have always believed that people who read books are intelligent. They don't just want a page-turning book. They want to learn things as well and what I've always tried to do with every book is to look at different aspects of human nature, aspects of psychiatry, aspects of what it is that makes us human. I try to learn new things myself and draw on things that I find interesting.

“For instance in the latest book, One Of Us Is Dead, I didn't realise that you could 3D print guns and that fascinated me. Over the course of the books I have introduced things that people didn't necessarily know, things like forensic gait analysis, the fact that the way that a human being walks is as unique as their fingerprints. And also four or five Grace books back I was approached by the commissioner of the Met who asked if I would put a super-recogniser into my next Grace so that police in other parts of the UK would recognise the value of having one, these extraordinary people who can pick out someone just by looking at their earlobe. It just completely fascinated me and I had a letter from somebody who read the book and told me that they had applied to become a super-recogniser for the police and had been accepted.”

The point is that Peter tries never to write the same book twice. In Dead Man's Time for instance it was the antiques world of Brighton & Hove that gave him the context; in Dead At First Sight it was internet romance fraud: “And I just got so many letters from readers saying thank you for writing about this. You wouldn't believe just how many people in Sussex have been fleeced.”

But the starting point for One Of Us Is Dead was quite something else: “At least once a fortnight somebody says to me ‘I've got an idea for a book that you are just going to want to write’ and I would say ‘Yeah, yeah, yeah’ and often it's a really nice idea but wouldn't necessarily make a novel. But I'll always listen but then one day the son of a friend of mine came up to me and told me that he had a story that I would absolutely want to write. He told me that he had been at a funeral at a country church in the pelting six months ago and there wasn't a seat to be had. It was absolutely packed and he turned up five minutes late and then halfway through he realised that six rows in front of him was somebody standing there whose funeral he had been to two years before and at whose funeral he had actually given the eulogy.”

The guy speaking to Peter hadn’t managed, after the funeral, to find the man who had seemingly returned from the dead, but for Peter: “It was definitely a story that I wanted to write!”